The use of gas-air mixers helps to provide a homogenous or proper ratio supply of gas and air to a premix burner in a heat exchanger system. A poorly mixed, improper ratio of gas and air can result in poor lighting, flame flashback, and poor combustion. Some HVAC systems accomplish mixing by use of an upstream blower assembly. However, such blower assemblies have drawbacks that prevent their use in residential applications. These drawbacks can include creating a positive pressure in burner and heat train creating potential safety concerns, space constraints, and expensive construction requirements.